1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition for use in a semiconductor production process for an IC or the like, a circuit board production for a liquid crystal, a thermal head or the like, the fabrication of an imprint mold structure, other photofabrication processes, a lithographic printing plate and an acid-hardenable composition, and further relates to an actinic-ray- or radiation-sensitive film, a photomask blank and a method of forming a pattern.
In the present invention, the term “actinic rays” or “radiation” means, for example, brightline spectra from a mercury lamp, far ultraviolet represented by an excimer laser, extreme ultraviolet, X-rays, soft X-rays, electron beams and the like. In the present invention, the term “light” means actinic rays or radiation.
2. Description of the Related Art
Heretofore, the microfabrication by lithography using a photoresist composition is performed in the process for manufacturing semiconductor devices, such as an IC and an LSI. In recent years, the formation of an ultrafine pattern in the submicron region or quarter-micron region is increasingly required in accordance with the realization of high integration for integrated circuits. Accordingly, the trend of exposure wavelength toward a short wavelength is seen. To now, an exposure equipment using an ArF excimer laser of 193 nm wavelength as a light source has been developed. Further, a method, known as a liquid-immersion method, in which the space between a projector lens and a sample is filled with a liquid of high refractive index (hereinafter also referred to as an “immersion liquid”) has progressed as a technology for enhancing the resolving power. Still further, the development of lithography technology using electron beams, X-rays, EUV light or the like, aside from the excimer laser light, is now being promoted. Accordingly, chemically amplified resist compositions that are effectively sensitive to various radial rays and excel in sensitivity, resolution, pattern shape, capability of suppressing any line edge roughness (LER) (roughness performance) and the like have been developed (see, for example, patent reference 1).
With respect to, in particular, the resolution and roughness performance, the smaller the pattern size, the greater the importance thereof. In the lithography using X-rays, electron beams or EUV, it is intended to form a fine pattern of several tens of nanometers (nm). Accordingly, the excellence in resolution and roughness performance are especially required in the lithography.
The electron beam (EB) lithography is positioned as the next-generation or next-next-generation pattern forming technology, and is indispensable as a method of processing a photomask blank for use in the fabrication of a photomask for semiconductor production.
In the EB lithography, it is known that the influence of electron scattering, namely, forward scattering in a resist film is lessened by increasing the acceleration voltage of EB. Therefore, in recent years, the acceleration voltage of EB tends to be increased. However, increasing the acceleration voltage of EB may lower the ratio of trapping of electron energy in the resist film, thereby lowering the sensitivity.
Moreover, increasing the acceleration voltage of EB, although lessening the influence of forward scattering, increases the influence of the scattering of electrons reflected by a resist substrate, namely, backward scattering. When it is intended to form an isolated pattern of large exposure area, this influence of backward scattering is markedly grave. Therefore, for example, an increase of the acceleration voltage of EB might lead to the possibility of a deterioration of the resolution of the isolated pattern.
In particular in the patterning of a photomask blank for use in semiconductor exposure, as a light shielding film containing a heavy atom, such as chromium, molybdenum or tantalum, is present in a layer under a resist, the influence of backward scattering attributed to a reflection from the resist underlayer is more conspicuous than in the application of a resist onto a silicon wafer. Therefore, when an isolated pattern is formed on a photomask blank, the influence of backward scattering is so grave that the possibility of resolution deterioration is high.
As a method for enhancing the resolution of an isolated pattern, the use of a resin containing a group capable of regulating the solubility of the resin is being studied (see, for example, patent reference 2). However, this has not yet fully satisfied the resolution and rectangularity of an isolated pattern.
Moreover, further enhancement of resolution is also required in the formation of a fine contact hole pattern.